Microwave amplifiers

ABSTRACT

A microwave amplifier has two electron guns for projecting two electron beams, each between a longitudinal meander structure disposed between the electron beams, and two longitudinal cooperating electrodes. At the opposite end of the amplifier from the electron gun are provided two pairs of beam receiving diodes, one pair for each beam, which amplify and provide an output representative of the beam current when radio frequency (R.F.) energy is coupled to the meander structure. The R.F. energy provides a transverse electric field between the meander structure and both co-operating electrodes so as to deflect the electron beams such that each electron beam lands upon its respective pair of beam receiving diodes.

O Unlted States Patent 1 1 1111 3,890,532 Esterson 1 June 17, 1975 15 MICROWAVE AMPLIFIERS 3,733,510 5/1973 Fiscker et a1. 315/3 [75] Inventor: ce Esterson, e m 3,749,961 7/1973 Bates et al. 315/3 England Prmzary Exammer-Saxfield Chatmon, Jr. [73] Assignee: English Electric Valve Company Attorney, Agent, or Firm-Baldwin, Wight & Brown Limited, Chelmsford, England [22] Filed: Oct. 3, 1973 ABSTRACT v [21] AppL NOJ 403,042 A microwave amplifier has two electron guns for projecting two electron beams, each between a longitudinal meander structure disposed between the electron [52] U.S. Cl. 315/3; 313/366; 315/36 beams, and two longitudinal cooperating electrodes. [51] Int. Cl ..'H0lj 23/16; H01 29/96 At h opposite d f the lifi f the electron [58] Field of Search 315/3, 3.5 X, 3.6; gun are provided two pairs f beam receiving diodes, 313/65 AB, 366; 357/31 one pair for each beam, which amplify and provide an output representative of the beam current when radio References Cited frequency (RF) energy is coupled to the meander UNITED STATES PATENTS structure. The R.F. energy provides a transverse elec- 3,005,128 10/1961 Goldberg et a1. 315/36 x Irie field between the meander Structure and both 3,090,886 5/1963 Ash 315/3.6 p rati g t d s 5 as to fl t h l tron 3,280,361 10/1966 Goldberg et a1. 315/3 beams such that each electron beam lands upon its re- 3,694,689 9/1972 Odenthal et al- 3 5/3 spective pair of beam receiving diodes. 3,725,803 4/1973 Yoder 315/3 3,732,456 5/1973 Buck 315/3 6 Claims, 3 Drawmg Flgures MICROWAVE AMPLIFIERS This invention relates to microwave amplifiers and more particularly to microwave amplifiers of the type where an electron beam is arranged to bombard a semiconductor diode which amplifies the current impinging on its surface.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows in a schematic form a known microwave amplifier.

FIG. 2 shows in detail a meander structure for use in a known microwave amplifier. I

FIG. 3 shows in schematic form a microwave amplifier in accordance with this invention.

In the figures, like numbers denote like parts.

BACKGROUND OF THE INVENTION Referring to FIG. I, the microwave amplifier shown therein has an evacuated envelope 1 within which is an electron gun assembly 2 comprising a cathode heater 3, a cathode 4, a focusing electrode 5 and an anode 6. The electron beam, shown schematically by broken lines 7, emerging from the gun assembly 2 passes between a plate electrode 8 and a meander structure 9. The electrode 8 and the meander structure 9 are longitudinally parallel to one another and also parallel to one another along the axis orthogonal to the beam axis. Coaxial connector 10 has its inner conductor connected to one end of the meander structure 9 and its outer conductor connected to the plate electrode 8, and a coaxial load termination 11 is connected to the other end of the meander structure 9 and electrode 8.

Perpendicular to the electron beam is a screen 12 having two apertures 13 therein. Situated behind the apertures 13 are two semiconductor diodes 14, 15 which are electrically insulated from one another and both of which are mounted in insulated manner on a heat sink 16. A coaxial transmission line 17 which terminates in a load (not shown) has its inner conductor connected to the diode 14 and its outer conductor connected to the diode 15. A DC. power supply (not shown) is connected across the diodes 14, 15 to provide a suitable bias voltage thereto.

The meander structure 9, which is shown orthogonally in FIG. 2 is an electrical conductor which, with electrode 8 sets up a transverse electric field in the space therebetween when RF. energy is applied from connector 10. The meander structure 9 is shaped and dimensioned such that it maintains a predetermined phase relationship between the transverse electric field and the electron beam as the electron beam travels towards the screen 12.

In operation, with an R.F. input to connector 10, the transverse electric field deflects the electron beam 7 so that electrons pass through the apertures 13 in dependence upon the RF. wave input, to impinge upon diodes 14, 15. The electron beam current impinging on each diode 14, 15 is amplified therein by a factor of approximately 1000 and taken as output from the line 17.

However, such known microwave amplifiers have been found to radiate R.F. energy in the direction of the arrow headed line Y in FIG. 1 with the result that useful power is lost. Furthermore, metallic or electromagnetically deflecting objects in the vicinity of the meander structure 9 tend to perturb the performance of the amplifier.

vided for each diode.

SUMMARY or INVENTION The present invention seeks to provide a microwave amplifier that substantially reduces the aforerrentioned defects. i

Accordingto this invention a microwave amplifier includes means for generating and projecting two electron beams; a meander structure longitudinally positioned between the two electron beams; two cooperating electrodes which are each longitudinally positioned Preferably each pair of co-operating electrodes are longitudinally parallel with the meander structure. Alternatively the co-operating electrodes diverge in correspondence with the divergence of the electron beam as it travels towards the pairs of beam receiving diodes provided therefor.

Preferably the co-operating electrodes are plate electrodes.

Preferably the beam receiving diodes nearest to the meander structure are both connected to one conductor ofa coaxial or strip transmission line and the diodes furthest from the meander structure are connected to the other conductor of the coaxial or strip transmission line.

The invention will now be described, by way of example, with reference to FIG. 3 which shows in schematic form a microwave amplifier in accordance with this invention.

Like parts of the microwave amplifier shown in FIG. 3 having like parts to those of the known amplifier previously described with reference to FIGS. 1 and 2 have been given like reference numerals.

Referring to FIG. 3, the electron gun assembly 2 comprises a further cathode 4', a further focusing electrode 5 and an anode 6' having an additional aperture to permit passage of an additional electron beam 7. Parallel to the meander structure 9 in both the longitudinal, electron beam, axis and the axis orthogonal thereto is a further plate electrode 8'. A screen 12' having four apertures 13 and 13' each of which are off-axis with respect to the electron beams 7, 7 replaces screen 12. Situated behind the apertures 13 are a further pair of semiconductor diodes l4, 15 which are also insulated from one another and across which there is also provided a suitable DC. bias voltage from the source not shown. Output from the diodes 14, l4, 15, 15 is taken via coaxial transmission line 17 with the diodes 14, 14' nearest to the meander line 9 being connected to the inner conductor of the line 17 and the diodes 15, 15 furthest from the meander line 9 being connected to the outer conductor of transmission line 17.

In operation the electron gun 2 potential is approximately l0KV, the plate electrodes 8, 8' are at earth potential, the screen 12' is arranged to be a few volts positive with respect to earth and the bias potential applied to the diodes is 300V at 5A. Approximately lW of RF. energy is applied to the meander structure 9 through connector to provide a transverse electric field between the structure 9 and electrodes 8, 8, so as to thereby deflect the electron beams 7, 7'. The electron beams 7, 7 are thus switched together between impinging upon diodes 14, 14 and diodes 15, in dependence upon the RF. input wave. Output current from the diodes 14, l4 15, 15 is taken via coaxial transmission line 17 to the load not shown.

Thus the invention provides a balanced arrangement which, while substantially suppressing spurious radiation from the meander line 9 and rendering the amplifier performance insensitive to metallic or electromagnetically deflecting conductors, substantially doubles the power output of the amplifier.

Although, as described above, the plate electrodes 8, 8 and the meander line 9 are parallel to one another in the longitudinal, electron beam, direction, it is to be understood that the electrode 8, 8' may be arranged to diverge as the electron beams 7, 7 diverge along the longitudinal axis towards the diodes 14, 15 and 14, 15 respectively. Also, the output line 17 may be what is known as a strip transmission line".

l claim:

1. A microwave amplifier including means for generating and projecting two electron beams; a meander structure longitudinally positioned between and common to the two electron beams; two co-operating electrodes which are positionedso that the two electron beams and said meander structure lie between them; two pairs of beam receiving diodes, one pair for each beam, so positioned that each electron beam travelling undeflected between the meander structure and one of said co-operating electrodes will pass between a corresponding pair of beam receiving diodes; and means for coupling R.F. energy to the meander structure, whereby in operation the R.F. energy produces a transverse electric field between the meander structure and each said co-operating electrode so as to deflect the two electron beams in opposite directions such that each electron beam impinges upon one diode of its respective pair of beam receiving diodes.

2. A microwave amplifier as claimed in claim 1 wherein an apertured screen is positioned in front of the beam receiving diodes, one aperture being provided for each diode.

3. A microwave amplifier as claimed in claim 1 wherein each pair of co-operating electrodes are longitudinally parallel with the meander structure.

4. A microwave amplifier as claimed in claim 3 wherein the co-operating electrodes are plate electrodes.

5. A microwave amplifier as claimed in claim 2 wherein the co-operating elelctrodes are plate electrodes.

6. A microwave amplifier as claimed in claim 2 wherein the beam receiving diodes nearest to the meander structure are both connected to one conductor of a coaxial or strip transmission line and the diodes furthest from the meander structure are connected to the other conductor of the coaxial line. 

1. A microwave amplifier including means for generating and projecting two electron beams; a meander structure longitudinally positioned between and common to the two electron beams; two cooperating electrodes which are positioned so that the two electron beams and said meander structure lie between them; two pairs of beam receiving diodes, one pair for each beam, so positioned that each electron beam travelling undeflected between the meander structure and one of said co-operating electrodes will pass between a corresponding pair of beam receiving diodes; and means for coupling R.F. energy to the meander structure, whereby in operation the R.F. energy produces a transverse electric field between the meander structure and each said cooperating electrode so as to deflect the two electron beams in opposite directions such that each electron beam impinges upon one diode of its respective pair of beam receiving diodes.
 2. A microwave amplifier as claimed in claim 1 wherein an apertured screen is positioned in front of the beam receiving diodes, one aperture being provided for each diode.
 3. A microwave amplifier as claimed in claim 1 wherein each pair of co-operating electrodes are longitudinally parallel with the meander structure.
 4. A microwave amplifier as claimed in claim 3 wherein the co-operating electrodes are plate electrodes.
 5. A microwave amplifier as claimed in claim 2 wherein the co-operating elelctrodes are plate electrodes.
 6. A microwave amplifier as claimed in claim 2 wherein the beam receiving diodes nearest to the meander structure are both connected to one conductor of a coaxial or strip transmission line and the diodes furthest from the meander structure are connected to the other conductor of the coaxial line. 